Image correction method, apparatus, article and image

ABSTRACT

An image correction method able to avoid error image. According to opposite properties of black and white, only the last few bits of the scanned digital signal are extracted for black correction, while only the first few bits of the scanned digital signal are extracted for white correction. Further, the most significant bit of the digital signal is 1 for white correction. Therefore, the unwanted LBB effect on the scanned image caused by dust or spots on the correction document is avoided. In addition, as only a few bits of the scanned digital signal are extracted, the requirement in memory capacity is reduced.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/173,788, filed on Jul. 15, 2008, which is a continuation ofU.S. patent application Ser. No. 10/064,612, filed on Jul. 31, 2002, nowU.S. Pat. No. 7,421,145, each of which is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

The invention relates in general to an image correction method, and moreparticularly, to an image correction method to help avoid error images.

DESCRIPTION OF THE RELATED ART

In terms of functionalities, the scanner is an intermediate between thephotocopier and the camera. In the past, the application of scanners isrestricted to special art work due to the very high cost. In recentyears, the rapidly growing computer technique and the active competitionin the market result in signification cost reduction for the scanners.Eventually, the scanner has become a popular peripheral of personalcomputers.

Depending on the price or functionality, scanners can be categorizedinto several types. Typically, scanners can be categorized into handheldscanner, sheet-feed scanner, card reader, film scanner and flatbedscanner. The flatbed scanner includes a glass flatbed on which thedocument to be scanned is disposed. By shifting the sensor, theinformation of the document is read. As the structure is not verycomplex and the method for using it is not difficult, plus theoutstanding function expandability, the flatbed scanners have become theapplication main stream for the current computers.

Basically, scanners are divided into black-and-white type and color typewith respect to color display, and reflective type and transparent typewith respect to the scanning method. The following uses a reflectivetype color scanner as an example to introduce the basic structure of ascanner. Referring to FIG. 1, the basic structure of a color scanner 10is shown. The color scanner 10 comprises a lamp 102, an optical system104, a charge-coupled device (CCD) 106, and an analog/digital (A/D)converter 108. Functions of various parts of the color scanner 10 arefurther described as follows.

When the lamp 102 is used as the light source of the color scanner 10,the light generated by the lamp 102 is incident on the document 110. Thelight is then reflected by the document 110 to project onto the opticalsystem 104. The lamp 102 can be a fluorescent lamp, a cold cathode raytube, or a light emitting diode array.

The optical system 104 consists of a reflection mirror 112 and a lens114. Being focused by the reflection mirror 112 and the lens 114, thelight reflected by the document 110 is reflected by the reflectionmirror 112, focused by the lens 114, and then incident on thecharge-coupled device 106.

The function of the charge-coupled device 106 includes converting thedetected light intensity into photocurrent, which is then stored in thestorage electrodes and converted into signal charges to generate variouspotential.

The analog/digital converter 108 converts the analog signal of thecharge-coupled device 106 into a digital signal, and transmits thedigital signal into a computer 118.

When the scanner is scanning a document or a picture, the non-uniformityof the lamp requires an image compensation operation. Generallyspeaking, a correction document is used for image correction. Forexample, for the reflective type scanning, a black correction documentand a white correction document are used for image correction. If thecorrection document contains any unwanted object thereon, the unwantedstreaking (LBB) effect is generated in the scanned image. Currently,there is no image correction method able to avoid such LBB effect.

SUMMARY OF THE INVENTION

The present invention provides an image correction method to avoid errorimages. According to black and white characteristics, only the last fewbits of a scanned digital signal are extracted during black correction.While performing white correction, only the first few bits of thescanned digital signal are extracted. The most significant bit of thedigital signal is set as 1. Therefore, the LBB effect in scanned imagecaused by dust or spot on the correction document is avoided. Further,as fewer bits are extracted while scanning the digital signal, thememory requirement is reduced.

The image correction method able to avoid error images provided by thepresent invention is suitable for use in a scanner. While performingblack correction, a first correction digital signal is obtained byscanning a first document. Only the last few bits of the firstcorrection digital signal are extracted. While performing whitecorrection, a second correction digital signal is obtained by scanning asecond correction document, and only first few bits of the secondcorrection digital signal are extracted. Meanwhile, the most significantbit of the second correction digital signal is set as 1.

In one embodiment of the present invention, the last few bits of thefirst correction digital signal are stored in a memory. The memoryincludes a random access memory (RAM).

In one embodiment of the present invention, the first few bits of thesecond digital signal are stored in a memory such as a random accessmemory.

In one preferred embodiment of the present invention, the firstcorrection document includes a black document.

In one preferred embodiment of the present invention, the secondcorrection document includes a white correction document.

In one embodiment of the present invention, the black correctionincludes the following steps. When the first correction signal isobtained by scanning the first correction document, an image extractiondevice is used to obtain the first correction analog signal. The firstcorrection analog signal is then converted into a first correctiondigital signal by the image extraction device. The image extractiondevice includes a charge-coupled device.

The step of performing white correction further includes the followingsteps. When the second correction signal is obtained by scanning thesecond correction document, the image extraction device is used toobtain the second correction analog signal. The second correction analogsignal is then converted into a second correction digital signal by theimage extraction device.

According to the above, the present invention provides an imagecorrection method able to avoid error images. According to two oppositecharacteristics of black and white, only the last few bits of thedigital signal obtained by scanning are extracted during blackcorrection. While performing white correction, only the first few bitsof the digital signal obtained by scanning are extracted, and the mostsignificant bit of the digital signal is configured as 1. Therefore, theLBB effect on the image caused by dust or spot on the correctiondocument is avoided. Further, in the digital signal obtained byscanning, fewer bits are extracted, so that the required memory capacityis reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as theinvention, the objects and features of the invention and furtherobjects, features and advantages thereof will be better understood fromthe following description taken in connection with the accompanyingdrawings in which:

Both the foregoing general description and the following detaileddescription are exemplary and explanatory only and are not restrictiveof the invention, as claimed.

FIG. 1 shows the basic structure of a color scanner; and

FIG. 2 shows the process flow of an image correction method for helpingto avoid errors in images according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Prior to the description of the embodiment, it should be noted thatalthough the embodiment is described using the scanning process for thereflection document as an example, for those skilled in the art, theinvention is also applicable to the scanning process for the transparentdocument.

Referring to FIG. 2, an image correction method able to avoid errorimages in one embodiment of the present invention is illustrated. In theimage correction method, firstly, whether a black correction or a whitecorrection is performed is determined in step s202. While performingblack correction, the scanner uses the lamp to radiate a light on afirst correction document. The light reflected by the document is thenincident on a reflection mirror of an optical system, and focused by alens of the optical system to obtain a first correction optical signal.An optoelectric conversion is performed to convert the first correctionoptical signal into an electrical first correction analog signal by animage extraction device (such as charge-coupled device). The firstcorrection analog signal is then converted into a first correctiondigital signal by an analog/digital converter. While performing blackcorrection, the response of the image extraction device is small, suchthat the first few bits of the first digital correction signal are zero,and only the last few bits (such as last 8 bits) are extracted. Thus,the LBB effect caused by dust or spot on the first correction documentis avoided. Further, the first correction document includes a blackcorrection document (s204). Only the extracted last few bits of thefirst correction digital signal are stored in a memory such as a randomaccess memory, so that the storage capacity requirement of the memory isreduced (s206).

When white correction is performed, the lamp of the scanner is incidenton the second document. The light is then reflected by the seconddocument, incident on the reflection mirror of the optical system, andfocused by the lens of the optical system to obtain a second correctionoptical signal. The second correction optical signal is converted intoan electrical second correction analog electric signal by optoelectricconversion via the image extraction device. The second correction analogelectric signal is converted into a second correction digital signal viathe analog/digital converter. While performing white correction, theresponse of the image extraction device is significant, so that the mostsignificant bit of the second digital correction signal has to be setas 1. Therefore, only the first few bits (such as first 8 bits) of thesecond correction digital signal are extracted. In this way, the LBBeffect caused in the scanned image by dust or spot on the secondcorrection document is avoided. The second correction document includesa white correction document (s208). The extracted first few bits of thesecond correction digital signal are stored in the memory such as therandom access memory. As only the last few bits of the second correctiondigital signal are stored in the memory such as the random accessmemory. As only the last few bits of the second correction digitalsignal are stored, the requirement in storage capacity of the memory isreduced (s210).

According to the above, the present invention uses the oppositecharacteristics of black and white to extract only the last few bits ofthe scanned digital signal for black correction and the first few bitsof the scanned digital signal for white correction. Meanwhile, the mostsignificant bit of the scanned digital signal for white correction is 1.Therefore, the LBB effect caused on the scanned image by dust or spot onthe correction document is avoided. Further, in the scanned digitalsignal, fewer bits are extracted to reduce the capacity requirement ofthe memory.

Other embodiments of the invention will appear to those skilled in theart from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples to be considered as exemplary only, with a true scope andspirit of the invention being indicated by the following claims.

1. An apparatus, comprising: means for obtaining a black correctiondigital signal by scanning a document during black correction, whereinthe black correction digital signal comprises a plurality of bits; meansfor extracting only a portion of the plurality of bits of the blackcorrection digital signal; and means for storing only the extractedportion of the plurality of bits of the black correction digital signalin a memory.
 2. The apparatus of claim 1, further comprising: means forobtaining a white correction digital signal comprising a plurality ofbits; and means for extracting only a portion of the plurality of bitsof the white correction digital signal.
 3. The apparatus of claim 2,further comprising means for setting a most significant bit of the whitecorrection digital signal to a value of one.
 4. The apparatus of claim2, further comprising means for storing only the extracted portion ofthe plurality of bits of the white correction digital signal in thememory.
 5. The apparatus of claim 1, wherein the document comprises ablack correction document.
 6. The apparatus of claim 1, furthercomprising: means for scanning the document to obtain a correctionanalog signal; and means for converting the correction analog signalinto the black correction digital signal.
 7. The apparatus of claim 6,wherein the means for scanning comprises a charge-coupled device.
 8. Anapparatus, comprising: a processing device configured to: scan a targetobject during black correction to obtain a black correction digitalsignal comprising a plurality of bits; extract only a portion of theplurality of bits of the black correction digital signal; and store onlythe extracted portion of the plurality of bits of the black correctiondigital signal in a memory; wherein a value of at least a particular bitof the plurality of bits of the black correction digital signal having amost significant bit position of the plurality of bits of the blackcorrection digital signal is discarded without being stored.
 9. Theapparatus of claim 8, wherein the processing device is configured to:obtain a white correction digital signal comprising a plurality of bits;and extract only a portion of the plurality of bits of the whitecorrection digital signal; wherein a value of at least a particular bitof the plurality of bits of the white correction digital signal having aleast significant bit position of the plurality of bits of the whitecorrection digital signal is discarded without being stored.
 10. Theapparatus of claim 9, wherein the processing device is configured to seta value of at least a particular bit of the plurality of bits of thewhite correction digital signal having a most significant bit positionof the plurality of bits of the white correction digital signal to one.11. The apparatus of claim 9, wherein the processing device isconfigured to store only the portion of the plurality of bits of thewhite correction digital signal in the memory.
 12. The apparatus ofclaim 8, wherein the target object comprises a black correctiondocument.
 13. The apparatus of claim 8, wherein the processing device isconfigured to: scan the target object to obtain a correction analogsignal; and convert the correction analog signal into the blackcorrection digital signal.
 14. The apparatus of claim 13, wherein thescan is performed using a charge-coupled device.
 15. A method,comprising: scanning a target object during black correction to obtain ablack correction digital signal comprising a plurality of bits;extracting only a portion of the plurality of bits of the blackcorrection digital signal; and storing only the extracted portion of theplurality of bits of the black correction digital signal in a memory;wherein a value of at least a particular bit of the plurality of bits ofthe black correction digital signal having a most significant bitposition of the plurality of bits of the black correction digital signalis discarded without being stored.
 16. The method of claim 15, furthercomprising: obtaining a white correction digital signal comprising aplurality of bits; and extracting only a portion of the plurality ofbits of the white correction digital signal; wherein a value of at leasta particular bit of the plurality of bits of the white correctiondigital signal having a least significant bit position of the pluralityof bits of the white correction digital signal is discarded withoutbeing stored.
 17. The method of claim 16, further comprising setting avalue of at least a particular bit of the plurality of bits of the whitecorrection digital signal having a most significant bit position of theplurality of bits of the white correction digital signal to one.
 18. Themethod of claim 16, further comprising storing only the portion of theplurality of bits of the white correction digital signal in the memory.19. The method of claim 15, wherein the target object comprises a blackcorrection document.
 20. The method of claim 15, further comprising:scanning the target object to obtain a correction analog signal; andconverting the correction analog signal into the black correctiondigital signal.